A typical missile includes multiple controllable steering fins spaced around the sides of a missile fuselage. The fins are rotatable to provide aerodynamic steering control during missile flight. The fins are coupled to rotatable shafts that extend into the fuselage and engage corresponding motors, generally through associated gear linkages that control the rotation of the fins.
Accurate flight of the missile depends on the proper function of the steering fins, and it is desirable to avoid damage to the controls when the missile is carried external to an aircraft or during pre-flight handling. Locking the steering fins in place when the missile is not in use reduces the possibility of damage and wear on the steering fins and related components. At the same time, the steering fins must be quickly and reliably released so that they can perform their steering function when the missile is launched.
A typical locking mechanism releases the steering fins through ignition of a small explosive charge. Explosive or pyrotechnic charges, even small ones, require special handling and care to ensure safety and reliability, but act quickly and typically enable the unlocking mechanism to be relatively small and compact.